Gusen was a subcamp of Mauthausen concentration camp operated by the SS between the villages of Sankt Georgen an der Gusen and Langestein in the Reichsgau Ostmark. Primarily populated by Polish prisoners, there were also large numbers of Spanish Republicans, Soviet citizens, and Italians. Initially, prisoners worked in nearby quarries, producing granite which was sold by the SS company DEST.

Mauthausen was a Nazi concentration camp on a hill above the market town of Mauthausen, Upper Austria. It was the main camp of a group with nearly 100 further subcamps located throughout Austria and southern Germany. The three Gusen concentration camps in and around the village of St. Georgen/Gusen, just a few kilometres from Mauthausen, held a significant proportion of prisoners within the camp complex, at times exceeding the number of prisoners at the Mauthausen main camp.